Resolving electron and muon $g\ensuremath{-}2$ within the 2HDM

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Resolving electron and muon $g - 2$ within the 2HDM

Sudip Jana, Vishnu P. K., and Shaikh Saad

Phys. Rev. D 101, 115037 – Published 29 June 2020

Abstract

Recent precise measurement of the electron anomalous magnetic moment (AMM) adds to the longstanding tension of the muon AMM and together strongly point toward physics beyond the Standard Model (BSM). In this work, we propose a solution to both anomalies in an economical fashion via a light scalar that emerges from a second Higgs doublet and resides in the $O (10) − MeV$ to $O (1) − GeV$ mass range yielding the right sizes and signs for these deviations due to one-loop and two-loop dominance for the muon and the electron, respectively. A scalar of this type is subject to a number of various experimental constraints, however, as we show, it can remain sufficiently light by evading all experimental bounds and has the great potential to be discovered in the near-future low-energy experiments. The analysis provided here is equally applicable to any BSM scenario for which a light scalar is allowed to have sizable flavor-diagonal couplings to the charged leptons. In addition to the light scalar, our theory predicts the existence of a nearly degenerate charged scalar and a pseudoscalar, which have masses of the order of the electroweak scale. We analyze possible ways to probe new-physics signals at colliders and find that this scenario can be tested at the LHC by looking at the novel process $p p \to H^{\pm} H^{\pm} j j \to l^{\pm} l^{\pm} j j + E_{T}$ via same-sign pair production of charged Higgs bosons.

Received 10 March 2020
Accepted 17 June 2020

DOI:https://doi.org/10.1103/PhysRevD.101.115037

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Electroweak radiative corrections Extensions of Higgs sector Hypothetical particle physics models Magnetic moment Particle interactions Particle phenomena

Particles & Fields

Authors & Affiliations

Sudip Jana ^1,*, Vishnu P. K.^2,†, and Shaikh Saad ^2,‡

¹Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
²Department of Physics, Oklahoma State University, Stillwater, Oklahoma 74078, USA

^*sudip.jana@mpi-hd.mpg.de
^†vipadma@okstate.edu
^‡shaikh.saad@okstate.edu

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Vol. 101, Iss. 11 — 1 June 2020

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Figure 1
One-loop (left) and two-loop (right) contributions to lepton AMMs arising from beyond-SM neutral scalars. The one-loop contribution due to the charged scalar is not presented here. For our choice of diagonal Yukawa couplings, the only term that contributes for the one-loop diagram corresponds to $ℓ^{'} = ℓ$ .
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Figure 2
Magnitudes of one-loop (dotted) and two-loop (dashed) contributions to $Δ a_{ℓ}$ ( $ℓ = e$ , $μ$ ) by the BSM states of the theory. Solid lines represent the total magnitude of $Δ a_{ℓ}$ by assuming negative two-loop contributions. The horizontal bands indicate the experimental $2 σ$ allowed region.
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Figure 3
Scalar mass splittings allowed by the $T$ parameter constraint in the 2HDM. The yellow and green shaded regions represent the $1 σ$ and $2 σ$ exclusion regions from the $T$ parameter constraint [19]. The horizontal and vertical grey shaded regions indicate the positivity criteria for $m_{H} > 0$ and $m_{A} > 0$ , respectively. Here, we set $m_{H^{\pm}} = 110 GeV$ .
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Figure 4
Representative Feynman diagram for the signal $p p \to τ^{+} τ^{+} j j + E_{T}$ at the LHC.
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Figure 5
The parameter space in Yukawa coupling ( $y_{l}$ , whrere $l = e$ or $μ$ ) vs mass ( $m_{H}$ ) plane consistent with both the electron and muon AMMs. The green (red) and yellow (pink) regions represent the experimental $1 σ$ and $2 σ$ bands for the electron (muon) AMM $Δ a_{e}$ ( $Δ a_{μ}$ ). The color shaded regions with solid boundary denote the excluded parameter space by current experiments: brown region from the electron beam-dump experiments [122, 123, 124]; cyan and light black regions from the dark-photon searches through $e^{+} e^{-} \to γ H$ process at KLOE [128] and BABAR [130] respectively; light brown region from the $e^{+} e^{-} \to μ^{+} μ^{-} H$ searches at BABAR [134]; blue shaded region from LEP [138]; purple region from CMS [137]. In this plot, we also present the projected sensitivities from several proposed experiments: heavy-photon searches (HPS) from JLab experiment (dashed purple line) [127]; dark-photon searches through $e^{+} e^{-} \to γ H$ process and $e^{+} e^{-} \to μ^{+} μ^{-} H$ process from Belle-II (dashed black and dashed light brown lines respectively) [132, 133]. The projected sensitivities for the signal $p p \to H^{\pm} H^{\pm} j j \to τ^{\pm} τ^{\pm} j j + E_{T}$ at the LHC for center of mass energy 14 TeV with integrated luminosity $L = 3 {ab}^{- 1}$ and also for the center of mass energy 27 TeV with integrated luminosity $L = 15 {ab}^{- 1}$ are shown by black dashed vertical lines. The $y_{e}$ coupling is independently constrained from electron beam-dump experiments [122, 123, 124], the dark-photon searches through $e^{+} e^{-} \to γ H$ process at KLOE [128], BABAR [130] and LEP [138] experiment; whereas the $y_{μ}$ coupling is constrained from the $e^{+} e^{-} \to μ^{+} μ^{-} H$ searches at BABAR [134] and LHC [137] experiments.
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Figure 6
The green (red) and yellow (pink) regions represent the experimental $1 σ$ and $2 σ$ bands for the electron (muon) AMM $Δ a_{e}$ ( $Δ a_{μ}$ ) in $y_{e} - y_{μ}$ plane consistent with all the experimental constraints. We set $m_{H} = 100 MeV$ (1 GeV) for the left (right) panel. These plots demonstrate the required values of the electron and muon Yukawa couplings for simultaneously explanations of $Δ a_{e}$ and $Δ a_{μ}$ for a fixed value of $m_{H}$ . It should be understood that as long as the Yukawa couplings are within the red (pink) and green (yellow) bands for the muon and the electron, respectively, a simultaneously solution to both $Δ a_{e}$ and $Δ a_{μ}$ are achieved within their $1 σ$ ( $2 σ$ ) experimental measured values.
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Physical Review D

covering particles, fields, gravitation, and cosmology

Resolving electron and muon $g - 2$ within the 2HDM

Sudip Jana, Vishnu P. K., and Shaikh Saad

Phys. Rev. D 101, 115037 – Published 29 June 2020

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Physical Review D

covering particles, fields, gravitation, and cosmology

Resolving electron and muon g−2 within the 2HDM

Sudip Jana, Vishnu P. K., and Shaikh Saad

Phys. Rev. D 101, 115037 – Published 29 June 2020

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Resolving electron and muon $g - 2$ within the 2HDM